Insulin resistance, which is a prevalent condition, has been associated with a cluster of metabolic disturbances that increase the risk of non-insulindependent diabetes mellitus and cardiovascular diseases. In this review article, the complexity of the etiology of insulin resistance is emphasized as it results from the interaction of genetic and environmental factors. Potential cellular defects underlying insulin resistance are discussed as well as the relation of impaired insulin action to dyslipidaemia and coronary heart disease.